Orbiters on future missions will examine the planet's environment even more precisely. They will search for evidence of water's existence both now and in the past, on the surface and underground. The history of water is key to all four science themes of the Mars Exploration Program: climate, geology, life, and preparation for human exploration.

Orbiters will also help identify scientifically interesting sites on the surface for further investigation and provide a knowledge of large rocks and other hazards at landing sites to be avoided.

Orbiters Can Assist in Communications and Navigation

Orbiters will also play a key role as communications relays for rovers, landers, balloons, and airplanes. For instance, it won't be practical for rovers, busy navigating hazardous terrain, to point their small antennas towards faraway Earth and transmit information. Instead, it will be easier for the rover to send data to a Mars orbiter, which in turn will precisely point a large antenna at Earth and communicate large volumes of images and other data.

Orbiters can also assist with navigation of other spacecraft approaching Mars. For example, Mars Reconnaissance Orbiter will carry a test camera that pinpoints the position of approaching spacecraft, helping navigators back on Earth know exactly how to direct the spacecraft for precision orbit insertion and landing.

Orbiters Can Assist with Sample Returns

Orbiters may also play a vital role in returning samples from the surface of Mars. Just as it is not efficient to communicate large volumes of science data directly from the Martian surface to Earth, it is not practical to launch a rocket containing samples from the Martian surface and expect it to navigate itself back to Earth and land safely. Instead, the preferred solution is to launch a small canister containing samples into orbit around Mars, have an orbiter rendezvous with and capture the canister, and then eject the spacecraft from Mars orbit back towards Earth.

See the technology section for information on technologies that will expand the capabilities of orbiters in the future, including propulsion and remote sensing.